Loop Patterns

Construction

Initialize variable before the loop starts
Perform computation on each loop item
Examine variable after the loop completes

Counting

Solution

count = 0

for i in [1, 3, 6, 10, 15, 21]:
    count = count + 1

print(count)

Sum

Solution

total = 0

for num in [1, 3, 6, 10, 15, 21]:
    total = total + num

print(total)

Counting and Summing

Helpful pattern to understand
Can be easily replaced by len and sum in simple cases

Mean

Solution

total = 0
count = 0

for num in [1, 3, 6, 10, 15, 21]:
    total = total + num
    count = count + 1

mean = total / count

print("Total:", total, "Count:", count, "Mean:", mean)

Could we compute the mean without using a loop?

Solution

nums = [1, 3, 6, 10, 15, 21]

mean = sum(nums) / len(nums)

print("Mean:", mean)

Word Count

How can we count the words in a string?

Maximum and Minimum

Sometimes we want to compare one value to others
Examples include finding a max or a min

Max

Solution

import math

nums = [1, 4, 7, 12, 3]
largest = -math.inf

for num in nums:
    if num > largest:
        largest = num

print(largest)

Min

Solution

import math

nums = [1, 4, 7, 12, 3]
smallest = math.inf

for num in nums:
    if num < smallest:
        smallest = num

print(smallest)

min function

Solution

import math

def min(nums):
    smallest = math.inf

    for num in nums:
        if num < smallest:
            smallest = num

    return num

Linear Search

Sometimes we want to find a specific value
This can be accomplished by checking items one by one

Check if a word has no vowels

Solution

word = input("Enter a word with no vowels:")
valid_word = True

for letter in word:
    for vowel in 'aeiou':
        if letter == vowel:
            valid_word = False

if valid_word:
    print("That's correct")
else:
    print("Your word included a vowel.")